As is well known to those skilled in the art, lubricating oils must be formulated, as by addition of various additives, to improve their properties.
In the case of lubricating oils typified by those employed in railway, automotive, aircraft, marine, etc. service, it is found that they become degraded during use due inter alia to formation of sludge which may be generated by deterioration of the oil or by introduction of undesirable components from other sources including the fuel or the combustion air. In order to maintain and improve the properties of the lubricating oil, various additives have heretofore been provided; and these have been intended to improve the viscosity index, dispersancy, oxidative stability, etc. Illustrative of such prior approaches is U.S. Pat. No. 4,089,794.
It is an object of this invention to provide an additive system which permits attainment of improved lubricating oils. Other objects will be apparent to those skilled in the art.